PROJECT SUMMARY/ABSTRACT Diabetes is considered to be one of the most widespread and devastating public health crises facing the United States today. In particular, the vast majority of the estimated 29 million affected individuals within the United States suffer from type 2 diabetes. Insufficient production of insulin by the beta cell can contribute significantly to the onset of type 2 diabetes; elucidating the biology of insulin secretion and the mechanism by which this beta cell dysfunction occurs is therefore critical to developing a more in-depth understanding of type 2 diabetes and informing new therapeutic strategies. Importantly, our lab and others have demonstrated that metabolic defects can drive beta cell dysfunction. For this reason, our long-term objective is to identify and explore the biology of novel regulators of beta cell metabolism. We have recently identified the Fe-S cluster protein BOLA3 as one such putative regulator. While little is currently known about BOLA3, it is thought to act as a mediator of multiple stages of aerobic respiration, including the TCA cycle and oxidative phosphorylation. Additionally, though BOLA3 canonically functions within the mitochondria, our preliminary data indicate that various peripheral tissues may secrete BOLA3 protein; and, furthermore, that BOLA3 can act exogenously on the beta cell to promote glucose-stimulated insulin secretion. We therefore propose to explore the role of BOLA3, both mitochondrial and secreted, in beta cell metabolism and function. In Aim 1 we will investigate the role of endogenous, mitochondrial BOLA3 in the context of a tissue-specific, conditional model of Bola3 knockout. Here we will determine the requirement for BOLA3 within the beta cell as it relates to glucose homeostasis, insulin secretion, aerobic respiration and metabolism, and cellular identity and maturity. In Aim 2 we will investigate the impact of exogenous, secreted BOLA3 on beta cell metabolism and function using an in vitro culture system. Here we will assess the effect of stimulation with recombinant BOLA3 protein on the global metabolic profile, including glycolysis and oxidative phosphorylation, of the beta cell. We will additionally determine the effect of stimulation with recombinant BOLA3 on both various known downstream target proteins of endogenous BOLA3 and lateral signaling cascades that are active during the process of insulin secretion, such as cAMP signaling. Through this study we expect to elucidate a previously unknown regulator of beta cell metabolism and function; these findings will contribute significantly to our understanding of beta cell biology. We further anticipate that the characterization of and research into this novel insulin secretagogue will have intriguing therapeutic implications.